Gibraltar's chief minister Fabian Picardo has said he has no intention of removing the reef.

But on Monday he indicated that new regulations would allow "sustainable" fishing by Spanish fleets in Gibraltar's territorial waters for the first time since they were barred in 2012, the spokesman added.

Mr Hague said this showed Gibraltar's "genuine willingness to resolve the fishing dispute".

But Spanish authorities have said Gibraltar had laid the blocks "without the necessary authorisation" in "waters that are not theirs", contravening environmental laws and damaging Spain's fishing industry.

In a statement issued after the call with Mr Cameron, Mr Rajoy said he had reiterated his desire to "seek a swift solution" to the row.

But he also said he had reiterated Spain's position that the "unilateral act of installing cement blocks in Algeciras Bay was unacceptable".